Rocket engines, such as those used on space missions, are costly to design and manufacture. In addition, there is a continuing and growing need for rockets capable of carrying payloads to space or near-Earth orbits. Consequently, manufacturers of such rocket engines are constantly seeking new ways to reduce the cost of producing the components which go into a rocket engine.
One such component is the rocket thrust chamber within which the propellants of the rocket engine are mixed, combusted and accelerated. Because of the extremely high temperatures of the propellants moving through the thrust chamber, the walls of the thrust chamber must be cooled in those applications which require sustained engine firings. Such cooling is typically accomplished by flowing a coolant through tubes or channels which form the inner surface of the thrust chamber.
A typical example of such thrust chambers is shown in U.S. Pat. No. 3,208,132 to Escher, which discloses a rocket chamber produced by forming coolant flow passages within two sheets by an explosive forming process. The formed sheets must be subsequently welded or brazed together to form individual flow passages, and the integrity of these welds is difficult to inspect. U.S. Pat. No. 3,190,070 to Neu discloses a rocket chamber cooling tube liner formed from a plurality of pre-formed coolant tubes that are inspectable, however, the tubes must be manufactured to close tolerances to ensure that the resulting brazed cooling tubes adequately shield the structural jacket of the chamber from the combustion products. Such tube forming typically requires multiple or progressive dies to produce each tube, and due to manufacturing tolerances, computers must often be used to select tubes (based on dimensions) from a large inventory of finished tubes to minimize tube-to-tube gaps in the cooling tube liner. The current method is thus both time consuming and labor intensive.
What is needed is a method of making a cooling tube liner which is simple, achieves the necessary tube-to-tube gap tolerances, is less labor intensive than the prior art, and is readily inspectable.